Switch to using spawn to properly treat errors during sync_state

Changes f1b9ac5a and 9f6ff7e3 were aimed at improving the robustness
of the sync_state method. However both missed switching from spawn_n
to spawn to properly deal with raised exceptions.

Change-Id: Ieda4a5ecca63de67d8a9757962e7e3383fd9c9ea
Related-bug: #1257514
Updates tox.ini to use new features

tox 1.6 allows us to skip the sdist step, which is slow. This does that.
It also allows us to override the install line. In this case, it's
important as it allows us to stop getting pre-release software we
weren't asking for.

Original patch by Monty Taylor, talked about here:
http://lists.openstack.org/pipermail/openstack-dev/2013-September/015495.html

Change-Id: I87f172cfcc44c9afff9c5162791d6c6b31972702
NVP plugin: Do backend router delete out from db transaction

Performing the NVP API operation from within a DB transaction
increases the risk of a deadlock between sqlalchemy and eventlet.

With this patch, the operation is moved outside of the db transaction
and appropriate mechanism are put in place for:
i) ensuring neutron db consistency in case of NVP failures
ii) avoiding deleting from backend if neutron logic does not allow it

This patch also synchronizes the routine for removing a router
gateway port from NVP.

Change-Id: I58d156e303e7a56ceb8c62766c192e154b0a3bb4
Closes-Bug: #1258150
Revert "move rpc_setup to the last step of __init__"

This reverts commit f691ebe03916a78cbf18017d628a28b17f147700.

Change-Id: Idc0bb0e4401e2561f2d8e3132f14df14b7537448
Partial-Bug: #1253896
Merge "Updates tox.ini to use new features"
Merge "Revert "move rpc_setup to the last step of __init__""
Imported Translations from Transifex

Change-Id: Ib37e90be421f09b9e9d3324f7b3152b87226ac99
Merge "NVP plugin: Do backend router delete out from db transaction"
Nicira: Fix core_plugin path and update default values in README

The following patch fixes the core_plugin path in the README file
which broke during the rename of quantum to neutron here ee3fe4e8.
This patch also updates a few of the default values and removes
the promise of adding support for multiple control clusters.

Issue reported by: Ben Lin <blin@nicira.com>

Change-Id: Ia46d80384efaa220685f98afa591177d00021362
Closes-bug: #1260550
Merge "Switch to using spawn to properly treat errors during sync_state"